The mitral valve is positioned in the heart left side, between the left atrium and the left ventricle. The most typical disease of the mitral valve is insufficiency or regurgitation which occurs when the valve leaflets do not coapt properly. Mitral valve repair by suturing a ring to reduce the annulus diameter is the procedure of choice to correct mitral regurgitation. With the use of current surgical techniques, most regurgitant mitral valves can be repaired or replaced with artificial valve prosthesis.
Currently, mitral valve repair requires an extremely invasive surgical approach that includes a sternotomy, cardio-pulmonary bypass, cardiac arrest, and an incision in the heart itself to expose the mitral valve. Such procedure is associated with high morbidity and mortality. A percutaneous device that can effectively treat the disease without the need for open heart surgery could greatly improve patient benefit and may include other patients that currently cannot be treated with surgery being too old or frail for such invasive procedure.
Most current surgical practices for mitral valve repair involve mitral valve annuloplasty and/or mitral valve valvuloplasty.
Surgical annuloplasty is a technique aimed to reduce the size of the fibrous tissue at the base of the mitral valve, called the annulus. Sometimes the annulus becomes enlarged, enabling blood to back flow up into the left atrium, through the gap between the two separated valve leaflets. The repair is done with sutures to make the opening smaller, helping the two leaflets meet and co-apt again when the valve closes.
Surgical valvuloplasty is a technique aimed to ensure proper closure of the valve leaflets. Leaflet function can be impaired as the result of prolapse of a leaflet due to ruptured chordae. The leaflet reconstruction is done by leaflet resection and reshaped with sutures. In most cases both annuloplasty and valvuloplasty is needed in order to regain optimal mitral valve function.
Due to the invasive nature of the mitral valve surgery, and the high risks involved in the procedure, many heart failure patients are poor surgical candidates. Thus, less invasive methods and devices to reduce mitral valve regurgitation would make this therapy available to many more patients.
US2004/102839, US2004/102840, U.S. Pat. No. 6,656,221, U.S. Pat. No. 6,718,985, U.S. Pat. No. 6,723,038 and US2004/073302 describe minimal invasive approaches to mitral valve annuloplasty, using percutaneous insertion of device into the left ventricle or into the coronary sinus, in order to decrease the annulus size.
U.S. Pat. No. 6,626,930 and U.S. Pat. No. 6,575,971 disclose a device and method of fastening two pieces of the valve leaflets together, improving competence of the valve.
US2004/243227, US2007/244554, US2008/262609, and US2009/0287304 describe percutaneous devices which attach to the valve annulus via anchoring mechanisms and contract, thereby reducing annulus diameter in a single step.
US2007/016286 discloses a transluminal collapsible heart valve designed to attach to the native annulus of the native regurgitating mitral valve and replace all in a single step. US2012/010700 provides a method for implanting a prosthetic valve apparatus that includes a one way valve and an expandable valve seating. The apparatus is anchored and secured in a newly created orifice near or at the center of the anterior valve leaflet.
Today it is possible to replace an aortic valve (the valve positioned between the left ventricle and aorta) with no surgery through newly developed percutaneous procedures. In these procedures an artificial collapsed valve is delivered through the arteries and positioned inside the diseased native valve, and then expanded to replace it. To date there is yet no acceptable analogous procedure that can do the same for the mitral or tricuspid valves.
Following the success of percutaneous replacement of the aortic valve, many attempts have been made to develop similar devices intended for percutaneous treatment of the mitral valve but due to the fact that this valve annulus is much bigger and amorphously shaped, and there are no lumen walls or calcific leaflets that may function as retaining surfaces like in the aortic valve, make it very difficult to prevent dislodgment of a valve expanded into place in the mitral position. Attaching a valve to the mitral annulus with anchoring features is very challenging for a percutaneous procedure and has not been very successful yet.
Devices that are attached to the mitral annulus and then collapsed to reduce its diameter need to be secured very tightly and accurately to the tissue in order to withhold the high forces that are required to reduce the annulus diameter.
Compared to the aortic valve percutaneous procedures, all the devices and procedures mentioned above have not been successful for the mitral valve yet.